<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<body>
<script type="text/javascript">
	
function show(x){
	alert(x == c);//true 
	//c undefined
	//x undefined
	var c = 10;
}
show();

</script>
</body>
</html>